StgTSO *t = cap->run_queue_hd;
ASSERT(t != END_TSO_QUEUE);
cap->run_queue_hd = t->_link;
- cap->run_queue_hd->block_info.prev = END_TSO_QUEUE;
+ if (t->_link != END_TSO_QUEUE) {
+ t->_link->block_info.prev = END_TSO_QUEUE;
+ }
t->_link = END_TSO_QUEUE; // no write barrier req'd
if (cap->run_queue_hd == END_TSO_QUEUE) {
cap->run_queue_tl = END_TSO_QUEUE;